The present invention relates to arc welding systems and more particularly to an electrode wire feeder therefor.
Gas metal arc (Mig) welding has several advantages over other types of welding including high deposition rates, speed, excellent weld quality, minimal distortion of the work piece and no stub loss. Typically, conventional Mig apparatus includes a torch and a wire electrode continuously fed from a supply reel or other source by an electrode wire feeder through the torch. The arc between the torch and the work piece continuously melts the wire electrode to form the weld puddle.
Heretofore, electrode wire feeders have included opposed feed rolls which exert sufficient pressure on the electrode wire passing therebetween and are driven by meshing gears to feed the electrode wire to and through the torch. In some instances, a single pair of opposed feed rolls are used, while in other instances two pairs of feed rolls are utilized in spaced relation along the feed path of the wire.
Because the electrode wire has to be threaded between the opposed feed rolls, provision must be made to form a gap therebetween for threading-up purposes and for closure of such a gap for operational purposes. Typically, one of the feed rolls of the pair or each of the pairs of feed rolls is mounted for movement between operative and inoperative positions to provide for formation and closure of such a gap. One example of such a feed roll arrangement has the stationary feed roll positively driven while the movable roll is rotated by contact with the driven roll. Such an arrangement is less than desirable because of slippage and uneven feeding of the electrode wire.
Accordingly, most electrode wire feeders have both feed rolls driven by meshing pinion gears on the shafts of the feed rolls. Because of the necessity of moving the feed rolls apart, it has heretofore been considered necessary to have both the feed rolls and their pinion gears adjacent and therefore exposed. These exposed gears are difficult to lubricate and are impossible to lubricate properly. In addition, such exposed gears collect dirt, debris and other foreign matter, all of which causes the gears to wear excessively and unevenly. Lastly, these exposed gears present a potential safety hazard to the operator and possibly others. Consequently, there has been a need for an electrode wire feeder which has the gearing thereof confined in a compartment containing a suitable lubricant while still providing for movement of the feed rolls between operative and inoperative positions.
This need was recognized in U.S. Pat. No. 2,272,158 which disclosed two pairs of feed rolls driven by gears enclosed in a gear box filled with a high temperature grease. However, the feed rolls were carried by shafts having fixed axes and the feed rolls were described as being expandable and retractable to provide the requisite gaps therebetween. Such an arrangement is cumbersome and has many other disadvantages and deficiencies.
With the foregoing in mind, it is an object of the present invention to provide an electrode wire feeder in which wire feed rolls are driven by gearing that is safely housed in a compartment and lubricated by a suitable lubricant and in which the feed rolls are movable between operative and inoperative positions.
This object is accomplished in accordance with the present invention by providing a housing defining an enclosed compartment in which a suitable lubricant may be confined. At least one pair of feed rolls is mounted on the housing exteriorly of the compartment by shafts that extend into the compartment and are driven by gearing therein. At least one of the feed roll shafts is mounted for movement toward and away from the other feed roll shaft for moving the feed roll thereon between operative and inoperative positions. Preferably, there are two pairs of feed rolls, with all of the feed rolls being gear driven, and one roll of each pair being movable. Also, the movable feed rolls are biased toward the other feed rolls when in the operative position.